The applicants have proposed to develop and test a light weight solid state imaging device (8x8 inches square) suitable for use in the operating room.Its specific application would be to assist the surgeon in locating tumor accumulations of radioactivity labelled monoclonal antibodies during surgical exploration. The unique feature of the imager would be that the detector would consist of an array of solid state elements rather than a single sodium iodide (NaI) crystal scintillator, as would be used in conventional (Anger-type) cameras. Because the imager would not use photomultiplier tubes or light pipes, its thickness and weight could be reduced. This would result in a configuration in which the imager can be suspended above and moved in any position over the operative field, while being maintained in a sterile environment in much the same manner as a operating room light or operating microscope. The Phase I effort would demonstrate feasibility by producing and evaluating a 5 cm(2) imager with 6 mm resolution, including a 25 element solid state detector array, amplifying and signal processing electronics and capability for video display and memory storage of the image.